Tallest of towers on tiniest of scales

Biomedical engineers have erected some of the tallest of towers on the tiniest of scales by getting biological molecules to do the labor.

“It’s like stacking Legos to make a tower,” said Ashutosh Chilkoti, associate professor of biomedical engineering at Duke University. The research is one step toward creating functional nanostructures out of biological materials.

The trick is harnessing some of biology’s most reliable workers — enzymes and catalysts — and making them follow the instructions for assembly. Chilkoti and his colleagues reported their results in the Journal of the American Chemical Society (Vol. 127 No. 41, Oct. 19, 2005, pp 14122-14123.)

The researchers created nanometer-scale patterns of gold on silicon, then coated the gold with short DNA strands. The entire complex was submerged in a solution containing the enzyme TdTase, a catalyst, and free-floating nucleotides, the building blocks of DNA.

The TdTase enzyme was of particular interest to the group because it can do more than just copy DNA. The enzyme can build DNA strands by joining together nucleotides whether or not they have matching DNA patterns.

The enzyme quickly took hold of the free nucleotide strands and attached them one piece at a time to the gold-tethered DNA, making the genetic strands as much as 100 times taller than they were at the outset.

The assembly, which occurred at room temperature in a humidity-controlled environment, should work with any type of DNA because the enzyme does not discriminate on the basis of DNA sequence, Chilkoti said.

“Developing the tools to harness biological reactions on the molecular scale opens a whole new arena for materials synthesis,” said team member Stefan Zauscher, assistant professor of mechanical engineering and materials science.

The DNA towers provide a type of scaffold, an ordered template, that bioengineers can use in the next step of building structures at the nanometer scale, a nanometer being one-billionth of a meter.

“When we can place molecules in the right configuration, then we can get them to function. At that point, we can design and create biological machines that accomplish something.” Chilkoti said.

Using molecular machines for manufacturing could automate the process of altering the material properties of substances to make them stronger, for example, or more durable. It also opens the door to designer materials with brand new properties.

Chilkoti received a 1998 Biomedical Engineering Research Grant from the foundation for work in molecular drug delivery.

From Whitaker Foundation

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